@fredericrose
You are correct. What @PatriciaV is saying is still not accurate way to calculate the average for the year. She said "the calculation should be (first + last) times months/12."
No,that's not how you calculate the average for the year.
You can use your formula ((first + last)/2) times months/12.
Or I actually just added each month balances and then divided by 12. The result would be the same in both cases.
You can also use Excel to calculate the average. Just enter each month balance and enter zero for the month you didn't have the mortgage, then pick AVG formula from Excel bar. It will calculate it for you. The result will be the same in either case.
